Chemical mechanical polishing solution

ABSTRACT

Disclosed is a chemical mechanical polishing solution containing cerium oxide, polyacrylic acid, polyether amine and water. In this invention polyether amine can serve as an additive to reduce the dishing amount of patterned wafer by negatively charged cerium oxide, and improve the efficiency of planarization.

TECHNICAL FIELD

The present invention relates to a chemical mechanical polishing solution, in particular to one chemical mechanical polishing solution.

BACKGROUND

Currently, chemical mechanical polishing (CMP) has become the most effective and mature planarization technology in the process of manufacturing micro-nano devices. In the process of manufacturing micro-nano devices, the process of Shallow Trench Isolation (STI) has become the mainstream isolation technology in recent years because of its outstanding performance of isolation, flat morphology and good locking performance.

In the polishing process of shallow trench isolation, the polishing rate of silicon oxide and silicon nitride by polishing solution generally has a high selection ratio. An exposed silicon nitride layer ideally can stop polishing as a barrier layer. And an over-polished silicon nitride layer will be recessed to form a so-called “Dishing”, resulting in the reduction of planarization efficiency. Therefore, there is a need to find a chemical mechanical polishing solution to improve the planarization efficiency.

DESCRIPTION

To solve the problem that negatively charged cerium oxide treated by acrylic acid is susceptible to dishing formation as a result of over-polishing, which exists in the prior art, the invention provides a chemical mechanical polishing solution, which includes cerium oxide, polyacrylic acid, polyether amine and water. The chemical mechanical polishing solution in this application cannot only keep a high polishing rate of silicon dioxide, but also reduce the dishing amount of patterned wafer by negatively charged cerium oxide.

Further, the concentration of the polyether amine is 1-80 ppm.

Further, the molecular weight of the polyether amine is 1,300-750,000.

Further, the concentration of the cerium oxide is 0.1 wt %-1.5 wt %, preferably 0.4 wt %.

Further, the concentration of the polyacrylic acid is 500-1,500 ppm, preferably 900 ppm.

Further, the chemical mechanical polishing solution also includes a pH regulator.

Further, the pH regulator is ammonia water, potassium hydroxide or nitric acid, acetic acid, hydrochloric acid and sulfuric acid.

Further, the pH of the chemical mechanical polishing solution is 4-8. If it is less than 4, the particle size becomes larger; if it is greater than 8, the effect of the chemical mechanical polishing with shallow trench isolation process is unsatisfactory.

In the present invention, ppm refers to the mass concentration expressed with the parts per million of solute mass to total solution mass, which is called ppm concentration. The wt % and the percentage of each component are mass percentage concentrations.

The reagents and raw materials used in the invention are commercially available.

Compared with the prior art, this invention has the advantages that the chemical mechanical polishing solution with polyether amine as an additive cannot only keep a high polishing rate of silicon dioxide, but also reduce the dishing amount on patterned wafer by negatively charged cerium oxide, thus improving the planarization efficiency. Preferably, with a molecular weight ranging from 1,300 to 750,000 and a content of 65 ppm or below, the polyether amine performs best in reducing the dishing amount.

DESCRIPTION OF THE DRAWING

FIG. 1 is the structure diagram of longitudinal section of patterned wafers

FIG. 2 shows the relationship between the polishing rate of silicon dioxide and the concentration of polyether amine (molecular weight 1,300) when the pressure is set at 4 psi.

DRAWING REFERENCE MARKS

1—bump, 2—pit, H1—bump line width, H2—pit width.

Embodiments

The advantages of an embodiment of the invention will be explained in detail with reference to the following drawing and embodiments.

In this invention, the chemical mechanical polishing solution prepared by mixing polyether amine and acrylic acid-treated cerium oxide can effectively control the dishing after polishing the dielectric layer substrate, and the method is simple, convenient and low in cost.

Embodiment

Preparation method: In this embodiment, reference embodiment is 0.4 wt % cerium oxide and the acrylic acid content is 530 ppm. In other embodiments and comparative embodiments, polyether amine with different molecular weights and contents is added to the reference embodiment, with pH value being adjusted to 4.5 by adding ammonia water (NH4OH) or nitric acid (HNO3), and mass percentage being complemented to 100% with water. Refer to Table 1 for details of components.

Polishing method: The polishing machine Mirra is used to polish TEOS blanks and patterned wafers. The polishing rate of silicon dioxide by the polishing solution in this application is tested on the TEOS blanks, and the inhibition of dishing increase by the polishing solution in this application is tested on the patterned wafers. The corresponding polishing conditions include: IC1010 polishing pad, polishing disk (Platten) and polishing head (Carrier) with rotating speed being set at 93 rpm and 87 rpm, respectively, pressure set at 4 psi, and flow rate of polishing solution set at 150 mL/min. The thickness of TEOS films is measured by using NanoSpec nonmetal film thickness measuring instrument (NanoSpec6100-300). The thickness of the blanks is obtained by measuring 49 points on the diameter line with equal intervals, starting from 3 mm away from the edge of the wafer. The polishing rate is the average value of these 49 points. The step height of the patterned wafer is measured by using a probe profiler (Bruker Nano's DETKAK XTL). FIG. 1 is the structure diagram of longitudinal section of patterned wafers in the prior art, where the patterned wafer has bump 1 and pit 2, salient point bump line width H1 and pit width H2. The measurement is performed at the bump line width H1/Pit width H2 of 500 um/500 um, 100 um/100 um, and 50 um/50 um, respectively.

TABLE 1 Relationship between Poly ether Amine (PEI-1.3 k) with Molecular Weight of 1,300 and Polishing Rate (RR) of Silicon Dioxide (TEOS) Blanks PEI-1.3 k TEOS RR (Å/min) Polishing solution (ppm) 1.5 psi 2 psi 3 psi 4 psi 1A (comparative 0 611 1,047 1,770 2,168 embodiments) 1B (embodiment) 2 605 1,007 1,718 2,308 1C (embodiment) 10 639 1,046 1,809 2,376 1D (embodiment) 50 624 985 1,687 2,241 1E (embodiment) 65 548 844 1,533 2,217 1F (embodiment) 80 493 784 1,167 1,552 1G (embodiment) 100 314 425 623 814

Table 1 shows that when the content of PEI-1.3k is 65 ppm or below, the polishing rate of silicon dioxide will hardly be affected as the content of PEI-1.3k increases. For example, when the polishing pressure is set at 1.5 psi, the polishing rates of silicon dioxide are 611, 605, 639, 624 and 548, corresponding to the content of PEI-1.3k of 0, 2, 10, 50 and 65, respectively; when the polishing pressure is set at 2 psi, the polishing rates of silicon dioxide are 1,047, 1,007, 1,046, 985 and 844, corresponding to the content of PEI-1.3k of 0, 2, 10, 50 and 65, respectively; when the polishing pressure is set at 3 psi, the polishing rates of silicon dioxide are 1,770, 1,718, 1,809, 1,687 and 1,533, corresponding to the content of PEI-1.3k of 0, 2, 10, 50 and 65, respectively; and when the polishing pressure is set at 4 psi, the polishing rates of silicon dioxide are 2,168, 2,308, 2,376, 2,241 and 2,217, corresponding to the concentration of PEI-1.3k of 0, 2, 10, 50 and 65, respectively. However, when the content of the PEI-1.3k reaches 80 ppm and 100 ppm, respectively, there exists significant difference between the polishing rates of silicon dioxide corresponding to different polishing pressures and the foregoing polishing rates. More specifically, the polishing rate of silicon dioxide is significantly reduced. The experiment data obtained when the polishing pressure is set at 4 psi in Table 1 are converted into FIG. 2 , where it can be seen intuitively that the polishing rates of silicon dioxide keep stable at the range from 2,168 to 2,376 A as the content of PEI-1.3k increases from 0 to 65 ppm, but once the content of PEI-1.3k reaches 80 ppm or higher, the polishing rate of silicon dioxide begins to fall. In other words, the range of 65-80 ppm is the critical point for the content of PEI-1.3k to exert influence on the polishing rate of silicon dioxide.

TABLE 2 Relationship between Polishing Rate of Silicon Dioxide and Molecular Weight and Concentration of Polyether Amine Molecular weight of PEI TEOS RR TEOS RR TEOS RR TEOS RR Polishing polyether concentration Å/min @ Å/min @ Å/min @ Å/min @ solution amine (ppm) 1.5 psi 2 psi 3 psi 4 psi 2A (comparative n/a 0 701 1,109 1,829 2,395 embodiments) 2B (embodiment) 1,300 50 624 985 1,687 2,241 2C (embodiment) 1,300 65 548 844 1,533 2,217 2D (embodiment) 2,500 45 765 1,037 1,778 2,233 2E (embodiment) 2,500 65 550 669 868 1,096 2F (embodiment) 70,000 45 726 1,106 1,696 2,163 2G (embodiment) 750,000 40 791 1,192 1,822 2,299 2H (embodiment) 750,000 65 667 785 1,014 1,273

Table 2 shows that as the molecular weight of polyether amine increases, the critical point of polyether amine concentration decreases to exert influence on the polishing rate of silicon dioxide. For example, compared with comparative embodiment 2A, when the same polishing rate is reached, the required concentration of polyether amine decreases as the molecular weight of polyether amine increases. Specifically, in Table 2, for example, when the molecular weight is 1,300 and the concentration is 65 ppm, the polishing rate does not decrease by more than 300 Å/min compared with that of the comparative embodiment 2A. When the molecular weight is 2,500, and the concentration is 65 ppm, the polishing rate decreases by more than 1,000 Å/min. However, when the molecular weight is 2,500, and the concentration is 45 ppm, the polishing rate does not decrease compared with that of the comparative embodiment 2A.

TABLE 3 Effect of Polyether Amine (Molecular Weight 1,300) as an Additive on Dishing Formation Dishing increase Dishing increase Dishing increase Polishing solution Additive @ (Å) 500/500 um @ (Å) 100/100 um @ (Å) 50/50 um 3A (comparative Not available 243 165 145 embodiments) 3B (embodiment) 65 ppm PEI 108 46 59 (Mw = 1,300)

Table 3 shows that polyether amine with a molecular weight of 1,300 (concentration of 65 ppm) can perform effective reduction of dishing formation at different measuring points (500/500 um, 100/100 um and 50/50 um), compared with the polishing solutions with absence of polyether amine.

TABLE 4 Effect of Polyether Amine with Different Molecular Weight as an Additive on Dishing Formation Dishing increase Dishing increase Dishing increase Polishing solution Additive @ (Å) 500/500 um @ (Å) 100/100 um @ (Å) 50/50 um 4A (comparative None 209 166 162 embodiments) 4B (embodiment) 50 ppm PEI (Mw = l,300) 152 125 112 4C (embodiment) 65 ppm PEI (Mw = l,300) 61 57 61 4D (embodiment) 40 ppm PEI (Mw = 2,500) 113 79 54 4E (embodiment) 45 ppm PEI 209 149 136

Table 4 shows that, as the content of polyether amine with a molecular weight of 1,300 increases from 50 ppm to 65 ppm, embodiment 4C performs with higher effectiveness in reducing the dishing than embodiment 4B does. However, when the concentration of PEI is kept constant, the less is the molecular weight of polyether amine, the more effective is the reduction of dishing. For example, when the concentration of PEI is 40 ppm, the molecular weight of PEI in embodiment 4D is 2,500, while that of PEI in embodiment 4F is 750,000, showing that the embodiment 4D performs more effectively than the embodiment 4F in reducing the dishing.

In conclusion, the chemical mechanical polishing solution containing polyether amine and acrylic acid-treated cerium oxide can effectively reduce the dishing in the polishing process of shallow trench isolation. With a molecular weight ranging from 1,300 to 750,000 and a content of 65 ppm or below, the polyether amine performs best in reducing the dishing amount. Meanwhile, all components of the chemical mechanical polishing solution in this application only need to be simply mixed, which is simple in operation and low in cost. Although the above specific embodiments of the present invention have been described in detail, they are only examples, and the present disclosure is not for limited to the embodiment described above. For those skilled in the art, any equivalent modification and substitution to the present invention is also covered in the present invention. Therefore, all these equivalent changes and modifications made without departing from the spirit and scope of the invention should be covered within the scope of the present invention. 

1. A chemical mechanical polishing solution, comprising cerium oxide, a polyacrylic acid, a polyether amine, and water.
 2. The chemical mechanical polishing solution according to claim 1, wherein a concentration of said polyether amine is 1-80 ppm.
 3. The chemical mechanical polishing solution according to claim 1, wherein a molecular weight of said polyether amine is 1,300-750,000.
 4. The chemical mechanical polishing solution according to claim 1, wherein a concentration of said cerium oxide is 0.1 wt %-1.5 wt %.
 5. The chemical mechanical polishing solution according to claim 1, wherein a concentration of said polyacrylic acid is 500-1,500 ppm.
 6. The chemical mechanical polishing solution according to claim 1, further comprising a pH regulator.
 7. The chemical mechanical polishing solution according to claim 6, wherein said pH regulator is selected from the group consisting of ammonia water, potassium hydroxide or nitric acid, acetic acid, hydrochloric acid and sulfuric acid.
 8. The chemical mechanical polishing solution according to claim 1, wherein a pH of the chemical mechanical polishing solution ranges from 4 to
 8. 9. The chemical mechanical polishing solution according to claim 5, wherein the concentration of said polyacrylic acid is 900 ppm.
 10. The chemical mechanical polishing solution according to claim 4, wherein the concentration of said cerium oxide is 0.4 wt %. 